In order to paint a frame buffer of a picture display unit uniformly with any data such as luminance data and color data, prescribed picture processing is required. Conventionally, in control for such picture processing, a single-access port or double-access port is used in order to connect the frame memory with a processor for control.
If a single-port memory is used as a frame buffer, the operation for painting the frame buffer, namely the writing of data into the frame buffer, is performed from a single random port. If a dual-port memory is used as a frame buffer, a serial-access port is used to read data out of the memory cell array. However, when a data register for serial access of a dual port memory is equipped only with a data output function, the writing of input data, such as paint information, into the memory cell array is carried out from a random port.
In a case where the single-port memory is used as the frame buffer, or in a case where the data register possesses solely an output function even if the dual-port memory is used as the frame buffer, the paint information from a processor must be written through a random port each time for every pixel when the frame buffer is painted with the predetermined information. Let T represent the time needed to write paint information in one specific row and column of the frame memory. In order to write paint information into an entire frame buffer composed of, e.g., 256.times.256 pixels, the processor must access the frame buffer 256.times.256 times, so that a time equivalent to 256.times.256 .times.T is required in order to write all the paint information. As a result, painting is very slow and the processor is subjected to a very heavy burden required for paint.
The present invention seeks to eliminate the foregoing problems of the conventional picture processing apparatus and its object is to provide a picture processing apparatus in which the burden on the processor can be lightened and paint information can be stored in the frame buffer at high speed.